The present invention is directed to a physical apparatus used to assist mechanically ventilating a patient. More specifically, the present invention provides non-invasive pressure changes outside a patient's chest wall, allowing mechanical ventilation without need for invasive endotracheal, orotracheal or tracheal intubation.
Under normal physiological conditions, humans breathe using “negative pressure ventilation.” In other words, a negative intrathoracic pressure is created by contraction of the intercostal muscles (between the ribs), upward and outward expansion of the ribs, and downward movement of the muscular diaphragm separating the thorax from the abdomen. All these changes act to expand both lungs and thus create a negative intrathoracic pressure. The pressure change enables gas to move from the outside atmosphere, through the human air passages, and into the deepest areas of the human lung. The natural tendency of the lungs to constrict similarly to a stretched rubber band, (elastic recoil), creates an inward intrathoracic pull, such that, as soon as the intercostal muscles relax, the ribs are pulled inward and downward, and the muscular diaphragm is pulled upward. These movements create a positive intrathoracic pressure, relative to the outside atmospheric pressure, thus forcing the gas out of the lungs through the human air passages, and back into the atmosphere.
By drawing on the natural biomechanics of human breathing, the present invention very closely simulates human respiratory mechanics and aids neonatal, pediatric and adult patients who require respiratory support or assistance.
Many different machines have been designed to deliver gas into the lungs by creating positive pressure outside the airways, and thereby forcing gas into the patient's airways. These machines provide lifesaving benefit, but are not without risks. For example, most “positive pressure ventilators” force gas through a small, artificial tube placed within the patient's trachea or airway, termed “invasive positive pressure ventilation,” because the patient's airway is penetrated or invaded by the artificial tube. Use of such a tube carries complications such as difficulty in proper placement, risks of dislodging, clogging, or causing infection. Additionally, the force with which each breath is delivered to the patient can lead to trauma to the lung tissue itself, including lung rupture or collapse.
More recently, “noninvasive positive pressure ventilation” has begun being practiced, which involves using a mask outside a patient's nose or mouth to deliver the positive pressure into the lungs. This greatly reduces the risks of improper placement, dislodging or clogging of the mask, and virtually eliminates the risk of severe infection due to contamination of equipment. However, such form of mechanical ventilation functions less than ideally because the gas cannot be directed solely into the lungs, but is rather forced into the back of the throat where the gas travels to both the lungs and stomach, the relative proportions of gas depending on the resistance of each pathway. Furthermore, several noninvasive positive pressure ventilators require the patient to remain confined to bed (e.g., Nasal Continuous Positive Airway Pressure (NCPAP) or Bilevel Positive Airway Pressure (BiPAP)), while others might allow the patient to sit up or be pushed in a wheelchair, but do not permit full mobility.
Negative pressure ventilators, e.g., iron lungs, are known in which a patient's body rests entirely within the chamber with only the patient's head protruding through a portal situated around the patient's neck. More recently, negative pressure ventilator “shells” have been developed that encompass only the patient's thorax and abdomen. For infants, negative pressure chambers are designed to house the entire body (excluding the head). Both the “shells” and chambers must be attached to a separate pressure ventilator via vacuum hose in order to function. However, such conventional chambers or ventilators suffer several disadvantages. For example, there is difficulty in observing a patient from all angles, with it also being cumbersome to access the patient through a door to the chamber. A great deal of space is required to permit the door to rest safely and securely on top of the ventilator chamber, when opened. Placement of the handle for the front access door to the ventilator chamber has resulted in confusion with locking mechanism for creation of the airtight seal of the access door. This could result in breaking of the access door handle and/or inadequate closure of the front shield and seal formation.
Difficulty has been encountered in including the patient's upper airway within the negative pressure chamber. Thus, the upper airway of a patient could be in danger of collapse during creation of the vacuum to assist the patient's breathing. Difficulty in accessing the interior of the chamber, e.g., during nonoperation, has made it difficult to easily clean and launder material in contact with the patient, e.g., an infant. Although ventilator chambers have been free-standing on the ground, a separate base or foundation has been required for practical functioning. Thus, an institution such as a hospital must provide such support for the chamber, while such support might not meet standards required by the Food and Drug Administration.
Difficulty has been encountered in providing an adequate seal around the patient's neck, especially in a small infant, resulting in a high percentage of vacuum leaks occurring at low vacuum pressure. This could activate alarms on the ventilator itself, forcing an operator to frequently stop and reset the ventilator at low pressures. Difficulty in monitoring and maintaining temperature and humidity inside the ventilator chamber has also been encountered.
Additional problems encountered with such ventilators include the need to stop and restart if a seal is broken for longer than an allotted period of time. Once seals have been well-established and the ventilator activated, it generally takes 20-30 seconds (based upon a breath rate of 20 breaths per minute and pressure −7 cm H20) to achieve the desired negative pressure. Providing sufficient staff to maintain such ventilators has also been difficult, while replacement parts were not readily available. As a result, lead time in clinical operation of such a ventilator after initial installation is often more than one month.
Developing the ability to utilize “noninvasive negative pressure ventilation” can eliminate many of the risks of the positive pressure ventilators.
Accordingly, it is an object of the present invention to improve effective and safe use of noninvasive negative pressure ventilation in assisting mechanical ventilation of a patient.
It is a more particular object of the present invention to provide a self-contained, noninvasive negative pressure mechanical ventilator created in the form of an air-tight covering about a patient's torso that will permit full mobility and comfort of the patient.
It is a further object of the present invention to improve respiratory mechanics and mobility, and thereby improve quality of life of patients requiring mechanical ventilation.